What are  and how to get their values?
Property definitions saved in blender rna.
When we define a prop with bpy.props the methods are akin to python's property method, extended to save the details in the blend files rna.  (From the geneticists mumbo jumbo)
All the things we define in the definition funcion, in this case FloatVectorProperty are stored here.  The value when set is stored as a custom property in the file.
Even tho we don't need to define Object.color it's very, very similar to  as if we defined
&gt;&gt;&gt; from bpy.props import FloatVectorProperty
&gt;&gt;&gt; bpy.types.Object.xcolor = FloatVectorProperty(
...         size=4,
...         default=(1, 1, 1, 1),
...         )

&gt;&gt;&gt; C.object.bl_rna.properties['xcolor']
&lt;bpy_struct, FloatProperty(&quot;xcolor&quot;) at 0x7fa4ee68d288&gt;

Which looks just like
&gt;&gt;&gt; C.object.bl_rna.properties[&quot;color&quot;]
&lt;bpy_struct, FloatProperty(&quot;color&quot;) at 0xc110c20&gt;

Instance value
&gt;&gt;&gt; C.object.color
bpy.data.objects['Cube.004'].color

&gt;&gt;&gt; C.object.color[:]
(1.0, 1.0, 1.0, 1.0)

Some defaults.
&gt;&gt;&gt; C.object.bl_rna.properties[&quot;color&quot;].default
0.0

&gt;&gt;&gt; C.object.bl_rna.properties[&quot;color&quot;].array_length
4

The array's default value
&gt;&gt;&gt; C.object.bl_rna.properties['color'].default_array
&lt;bpy_float[4], FloatProperty.default_array&gt;

&gt;&gt;&gt; C.object.bl_rna.properties['color'].default_array[:]
(1.0, 1.0, 1.0, 1.0)